Drawing of organic high polymers



Oct. 23, 1956 A. FRIEDERICH 2,768,057

DRAWING OF ORGANIC HIGH POLYMERS- Filed Feb. 10, 1955 INVENTOR ALFRED FR/EDER/CH ATTORNEYS United States Patent 2,768,057 DRAWING OF ORGANIC HIGH POLYMERS Alfred Friederich, Hamburg-Hochkamp, Germany, as-- This invention relates to improvements in the drawing of organic high polymers. The invention more particularly relates to the continuous stepwise drawing of strands of organic high polymers which are cold drawable and which show linear orientation in X-ray analysis after cold drawing.

Various proposals have been made for drawing strands of cold drawable organic high polymers in a plurality of stages rather than in single operation.

The use of a plurality of drawing stages is of particular interest if the drawing operation is not limited to a monofil or to a thin individual strand consisting of a plurality of filaments, but rather is effected on a thicker tow as, for example, is used in the production of cut fibers. Thus, for example, it has been suggested to subject the predrawn strands to a subsequent drawing operation in a second stage in heated swelling agents or solvents, or else in an atmosphere of superheated steam.

One object of this invention is a new and improved method for the drawing of cold drawable organic high polymer strands which show linear orientation in X-ray analysis after the cold drawing.

A further object of this invention is a new and improved method for drawing cold drawable organic high polymer strands which allows the drawing and extremely ethcient washing out of the insufliciently polymerized portions of the strands in a single operation.

A still further object of this invention is an improved aparatus for the multistage drawing of cold drawable organic high polymer strands. These, and still further objects, will become apparent from the following description read in conjunction with the drawing which shows a diagrammatic side elevation of an embodiment of a multistage drawing apparatus in accordance with the invention.

The strands which may be treated in accordance with the invention comprise any organic high polymers which may be cold drawn and which show a linear orientation in X-ray analysis after the drawing operation. Among the most notable of these cold drawable organic high polymers are polyamides and polyesters having a molecular weight above 10,000. The polyamides constitute the various known types of nylon, while the polyesters are designated as Dacron.

While the process in accordance with the invention is applicable for the treatment of cold drawable organic high polymer strands in any form ranging from the thinnest rnonofilament to the thickest tow, the invention is specifically intended for the treatment of the relatively heavier tow composed of numerous single strands and having a total weight of, for example, 50,000 to 1,000,000 denier.

Referring to the drawing, a multiple number of undrawn cold drawable high organic polymer strands as, for example, undrawn nylon or Dacron strands or filaments are passed through the reed or comb 2 as, for example, from bobbins. After passing through the reed 2, the strands 1 are combined into the tow 3.

The tow 3 passes around the lower side of the roller 4, between the rollers 4 and 5, around the upper side of the roller 5 and around the lower side of the roller 7. The roller 4 has a soft rubber surface and is pressed by means of the weighted lever 6 into surface contact with the roller 5 so that the tow 3 passing therebetween will be held along with all its individual strands.

The tow 3 is then passed through the roller system 8, 9, 10, passing between the rollers 9 and 10. The roller 10, similar to the roller 4, has a peripheral surface of soft rubber and is pressed by the weighted lever 10 in surface contact with the roller 9.

The rollers 5 and 7, 8 and 9 are driven, while the rollers 4 and 10 are idler rollers which prevent slippage of the tow 3 or the individual strands thereof, with respect to the rollers.

The rollers 8 and 9 are driven at a greater peripheral speed than the rollers 5 and 7 so that the tow 3 passing therebetween is subjected to a cold drawing.

This cold drawing is generally effected at about room temperature, though a slight heating may occur due to the drawing itself. Generally, the temperature of the tow 3 at the roller 5 is no more than 3035 C. and it is not necessary to cool or heat the strand. The temperature, however, is not critical and the cold stretching operation may be effected over a wide range of temperature as, for example, between about 0l00 C.

The difference in the peripheral speeds at which the rollers 5 and 7 and the rollers 8 and 9 are driven should be such that the tow 3 passing therebetween is drawn to about 2.5 to 4.5 and preferably to 3.5 times its original length.

After the cold drawing operation, the tow 3 passes from between the rollers 9 and 10 under the roller 12 through the bath 14 around the roller 13 between the rollers 13 and 15 and around the roller 15. The roller 15 has a soft rubber peripheral surface and is pressed by the weighted lever 16 in surface contact with the roller 13.

The bath 14 is a washing bath which serves the purpose of washing the unreacted monomers from the polymer material. For this purpose, water is generally used as a solvent for reasons of economy. The water preferably additionally contains a small amount of any conventional wetting agent so that the bath acts as a swelling bath. The bath may, for example, contain about 15% by weight of any conventional wetting agent as, for example, the known sulfonation products such as turkey red oil.

If the bath is at too low a temperature, the monomer will not be sufficiently washed out. On the other hand, it is not practical to use temperatures above 100 0, since the same would necessitate special apparatus to prevent boiling off of the water. The bath should therefore be preferably maintained at a temperature just below the boiling point, as, for example, at a temperature of about 60-100" C. and preferably at about C.

In accordance with the invention it has been found that the bath can only act properly upon the strands if they are passed through the liquid under the slightest possible tension and subjected to final drawing only after the action, as, for example, the swelling in the untensioned condition, has been terminated. The rollers 12 and 13 are therefore driven at a peripheral velocity which is about 10-25% less than that of the rollers 8, 9 and 10. The tow thus passes through the bath 14 in substantially untensioned condition. The rubber coated roller 15 serves to squeeze off the excess liquid from the strand as the same passes out of the bath.

From the roller 15 the tow 3 passes over the heated rail 17 which is heated in any conventional manner, as, for example, by superheated steam coils, electric resistant coils, hot gases, or the like. Upon passing over this rail 17 the strand is dried as, for example, to moisture content of about 3-12 and preferably about 510%.

In addition to the drying, the strand is heated to a temperature above C. and below the melting point and softening point of the materials. The heating is preferably effected to a temperature of about 25100 C. below the melting point as, for example, a temperature of about 125150 C.

The strand is then passed through the roller system 18, 19, 20 passing between the rollers 18, 19 and 20.

The roller 20 which has a peripheral surface of soft rubber is pressed in contact with the roller 19 by means of the weighted lever 21 to hold the strand therebetween.

The rollers 18, 19 and 20 are driven at a greater peripheral speed than the rollers 13 and 15 so that the strand is subjected to a drawing therebetween. The velocity of the rollers 19 and 18 should be about 15-30% higher than the roller 8 so that the tow is stretched up to 11.8 times its length as it leaves the bath 14, and preferably to about 1.5 times its length.

While it is preferable that the tow or strand actually be elongated between the roller groups 13, 15, 18, 19 and 20, the same is not essential and the tow or strand may actually only be tensioned between these roller groups without any true elongation. This tensioning without actual elongation should be effected when the tow or strand has been drawn to its maximum elongation between the roller groups 4, 5, 7, 8, 9, 10. The term tensioning as used in the claims is intended to designate both the maintaining of the tow or strand under tension and the actual elongation, i. e. drawing, thereof.

The drawing operation between the rollers 13 and 15 and the rollers 18, 19 and 20 is effected while the strand is at a substantially higher temperature than when drawn for the first time between the rollers, 4, 5 and 7 and the rollers 8, 9 and 10. The temperature of this stretching should be in excess of 100 C. and substantially below the melting point of the material as, for example, between 25 and 100 C. therebelow. It has been found preferable to effect the stretching at temperatures between about 125 and 150 C.

The tow 3 coming from the roller 20 may be collected as, for example, by winding in the conventional manner or may be passed through additional baths and stretching apparatuses corresponding to the portion of the apparatus illustrated from the bath 14 and roller 12 to the roller 19.

In no case can the total elongation of the strand or cable be effected beyond its elongation limit, as obviously to do so would cause breakage. The total elongation of the strand or cable in all of the combined drawing operations should preferably be effected just to the elongation limit which is generally about 4.5 times the original length.

As contrasted to the prior known drawing and swelling bath treatments of cold drawable organic high polymers the process in accordance with the invention allows the drawing operation and swelling bath treatment to be effected in a single operation with an extremely efficient washing out of'the insufficiently polymerized material from the threads in the swelling bath. This is of particular importance in connection with the treatment of 6-nylon or perlon in which the polymerized mass still contains about of non-polymerized or insufficiently polymerized material.

The following example is given by way of illustration and not limitation:

EXAMPLE A tow of a total thickness of about 810,000 denier and consisting of about 60,000 filaments of a polymer of e-amino-capro-lactam, which is commonly known as 6- nylon or perlon is wound together from 704 bobbins and passed through an apparatus corresponding to the apparatus shown in the drawing. The rollers 5 and 7 are driven at a peripheral velocity of about 35 meters per minute and the rollers 8 and 9 are driven at a peripheral velocity of about 135 meters per minute. The tow is drawn out to a total weight of about 180,000 denier with the individual filaments having a thickness of about 3 denier. The tow is then passed through the bath 4 which contains water at a temperature of about C. and contains about 0.2% by weight of a wetting agent known under the trade name of Nekal which comprises isopropylnaphthalene sulfo acid sodium. The tow as it passes through the bath 14 is in substantially untensioned condition. As the tow passes between the rollers 13 and 15 having a peripheral velocity of meters per minute the liquid from the bath is squeezed out. The tow then runs over the arched heating rail 17 on which it is heated to a temperature of about 180 C. after evaporation of the moisture. At the same time, the tow is subjected to a final drawing effected by the rollers 18, 19 and 20 which rotate at a greater peripheral velocity than the roller 13 as, for example, a velocity of about meters per minute. The final weight of the drawn capillary determined on the cut fiber is 2.8 denier and the strength is 59 when measured in accordance with the Reich Convention Method.

I claim:

1. Process for the drawing of cold drawable organic high polymer strands which comprises the steps of: (a) cold drawing such a strand; (b) passing the strand through an aqueous washing bath in substantially untensioned condition; (0) drying the strand, and (d) tensioning the strand at a temperature above about 100 C. and at least about 25 below the melting point thereof.

2. Process according to claim 1, in which said strand comprises a tow having a total weight between about 50,000 and 1,000,000 denier.

3. Process according to claim 1, in which said cold drawing is effected by stretching the strand to about 2.5-4 times its original length.

4. Process according to claim 3, in which said cold drawing is effected by stretching the strand to about 3.5 times its original length.

5. Process according to claim 1, in which said aqueous washing bath is at a temperature of about 60100 C.

6. Process according to claim 5, in which said aqueous washing bath is a swelling bath containing a wetting agent.

7. Process according to claim 1, in which said drying is effected to a moisture content of about 312%.

8. Process according to claim 1, in which said tensioning in step (d) is effected by stretching the strand up to 1.8 times its length prior to this step.

9. Process according to claim 8, in which said tensioning in step (d) is effected at a temperature of about 125-150 C.

10. Process according to claim 1, in which said steps are effected in substantially continuous operation.

11. Process according to claim 1, in which said cold drawable organic high polymer is a member selected from the group consisting of nylon and Dacron.

12. Process for the drawing of cold drawable organic high polymer strand which comprises the steps of: (a) cold drawing such a strand by stretching it to about 2.5 to 4.5 times its original length; (b) passing the strand through an aqueous swelling bath at a temperature of about 60-100 C.; (c) drying the strand, and (d) tensioning the strand at a temperature above 100 C. and at least about 25 C. below the melting point thereof by stretching up to about 1.8 times its length prior to this step.

13. Process according to claim 12, in which said cold drawing step (a) is effected by stretching the strand to about 3.5 times its original length and in which the said tensioning step (d) is effected by stretching the strand to about 1.5 times its length prior to this step.

14. Process according to claim 12, in which said strand is a tow having a total weight between about 50,000 and 1,000,000 denier.

15. Process according to claim 14, in which said cold drawable organic high polymer is a member selected from the group consisting of nylon and Dacron.

No references cited. 

1. PROCESS FOR THE DRAWING OF COLD DRAWABLE ORGANIC HIGH POLYMER STRANDS WHICH COMPRISES THE STEPS OF; (A) COLD DRAWING SUCH A STRAND; (B) PASSING THE STRAND THROUGH AN AQUEOUS WASHING BATH IN SUBSTANTIALLY UNTENSIONED CONDITION; (C) DRYING THE STRAND, AND (D) TENSIONING THE STRAND AT A TEMPERATURE ABOVE ABOUT 100* C. AND AT LEAST ABOUT 25* BELOW THE MELTING POINT THEREOF. 